A highly reliable ground connection on the vehicle chassis is used to safely supply an airbag control unit. On the control unit side, the provided chassis ground is generally connected to the circuit board via redundant electrical connections (e.g., screw connections, press-fit connections). The variant of the ground connection via the airbag power cable with the aid of one or multiple plug connections, combined with a press-fit or solder connection to the circuit board, is also used.
The positive supply line (KL15R, KL15, UBAT, etc.) is generally provided singularly or redundantly via the airbag power cable with the aid of one or multiple plug connections, combined with a press-fit or solder connection to the circuit board. The electrical properties of the airbag supply connection do not facilitate a safe self-diagnosis at a sufficiently high control unit supply voltage. In particular, there is no information on how the supply voltage behaves when more power is needed from the control unit. Intact supply connections normally guarantee supply inner resistances of (100 . . . 400) mΩ. These resistances are essentially determined by the copper resistors of the supply lines and the contact resistors. The share generated by the inner resistances of the vehicle battery or the generator (generator controller) is very low (approximately 10%).
Today, the error detection in the airbag supply network is limited to serious errors, such as generator controller failure, battery failure and interrupted supply line. This takes place through constant monitoring of the supply voltage with the aid of error detection in the case of undervoltage and overvoltage as well as service measures that provide a check of ground connections to the vehicle chassis.